THE EFFECT OF GULL ROOST DETERRENCE ON ROOST OCCUPANCY, DAILY GULL MOVEMENTS AND WINTERING WILDFOWL

Daily gull movements between feeding and roosting sites may present a major hazard to aircraft. One option to avoid this problem is to deter gulls from using certain favoured roosting sites. This may be difficu lt as the gulls usually roost on water. We assessed whether a large gu ll roost, at a reservoir near Oxford, UK, could be moved by using tape d distress calls and pyrotechnics without causing significant disturba nce to wintering wildfowl. Gull movements were monitored during 3 dete rrence trials by making weekly counts at several sites. These were com pared with seasonal trends in gull numbers at a roost beyond the influ ence of these operations. Observations and counts were used to investi gate the effects on wildfowl. These standard deterrence techniques pre vented roost formation so long as an alternative roost site was availa ble; they failed when alternative sites were frozen. Hence the pattern of gull movements in the area was considerably altered by their denia l from this important roost. Gull roost deterrence caused no detectabl e reduction in numbers of any other species, either at the reservoir o r in the Oxford area as a whole.